linux-kernel - Re: [PATCH v2 8/8] x86, kcsan: Enable KCSAN for x86

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Date:   Tue, 22 Oct 2019 13:59:22 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Marco Elver <elver@...gle.com>
Cc:     akiyks@...il.com, stern@...land.harvard.edu, glider@...gle.com,
        parri.andrea@...il.com, andreyknvl@...gle.com, luto@...nel.org,
        ard.biesheuvel@...aro.org, arnd@...db.de, boqun.feng@...il.com,
        bp@...en8.de, dja@...ens.net, dlustig@...dia.com,
        dave.hansen@...ux.intel.com, dhowells@...hat.com,
        dvyukov@...gle.com, hpa@...or.com, mingo@...hat.com,
        j.alglave@....ac.uk, joel@...lfernandes.org, corbet@....net,
        jpoimboe@...hat.com, luc.maranget@...ia.fr, npiggin@...il.com,
        paulmck@...ux.ibm.com, peterz@...radead.org, tglx@...utronix.de,
        will@...nel.org, kasan-dev@...glegroups.com,
        linux-arch@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-efi@...r.kernel.org, linux-kbuild@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, x86@...nel.org
Subject: Re: [PATCH v2 8/8] x86, kcsan: Enable KCSAN for x86

On Thu, Oct 17, 2019 at 04:13:05PM +0200, Marco Elver wrote:
> This patch enables KCSAN for x86, with updates to build rules to not use
> KCSAN for several incompatible compilation units.
> 
> Signed-off-by: Marco Elver <elver@...gle.com>
> ---
> v2:
> * Document build exceptions where no previous above comment explained
>   why we cannot instrument.
> ---
>  arch/x86/Kconfig                      | 1 +
>  arch/x86/boot/Makefile                | 2 ++
>  arch/x86/boot/compressed/Makefile     | 2 ++
>  arch/x86/entry/vdso/Makefile          | 3 +++
>  arch/x86/include/asm/bitops.h         | 6 +++++-
>  arch/x86/kernel/Makefile              | 7 +++++++
>  arch/x86/kernel/cpu/Makefile          | 3 +++
>  arch/x86/lib/Makefile                 | 4 ++++
>  arch/x86/mm/Makefile                  | 3 +++
>  arch/x86/purgatory/Makefile           | 2 ++
>  arch/x86/realmode/Makefile            | 3 +++
>  arch/x86/realmode/rm/Makefile         | 3 +++
>  drivers/firmware/efi/libstub/Makefile | 2 ++
>  13 files changed, 40 insertions(+), 1 deletion(-)

> diff --git a/drivers/firmware/efi/libstub/Makefile b/drivers/firmware/efi/libstub/Makefile
> index 0460c7581220..693d0a94b118 100644
> --- a/drivers/firmware/efi/libstub/Makefile
> +++ b/drivers/firmware/efi/libstub/Makefile
> @@ -31,7 +31,9 @@ KBUILD_CFLAGS			:= $(cflags-y) -DDISABLE_BRANCH_PROFILING \
>  				   -D__DISABLE_EXPORTS
>  
>  GCOV_PROFILE			:= n
> +# Sanitizer runtimes are unavailable and cannot be linked here.
>  KASAN_SANITIZE			:= n
> +KCSAN_SANITIZE			:= n
>  UBSAN_SANITIZE			:= n
>  OBJECT_FILES_NON_STANDARD	:= y

Not a big deal, but it might make sense to move the EFI stub exception
to patch 3 since it isn't x86 specific (and will also apply for arm64).

Otherwise this looks good to me.

Thanks,
Mark.